Patent GB-526308-A (GB)
Title: Improvements relating to safety means for sheet metal working presses or the like
IPC: B30B15/28
Filed: 1939-03-13
Abstract: 526,308. Metal-working presses ; clutches ; gearing for stopping and starting. GLASNER, R. W. March 13, 1939, No. 7992. [Class 83 (iv)] [Also in Group XXIV] In a sheet metal working press having a heavy reciprocating press head operated from a driving shaft through a clutch, the drive and clutch are connected to one another and to a locking means for the driving shaft by means such that when the drive is cut off, as by switching off a motor, the clutch is automatically opened and the lock is automatically engaged. The press comprises a bed above which is mounted a slide adapted to be driven by eccentrics from a shaft which may be rotated by a belt driven pulley or flywheel or may be braked by a connected clutch and brake mechanism actuated by fluid supplied to a cylinder located between the clutch and brake as described in Specification 526,307, [Group XXIV]. When the shaft is stationary, pins 68, Fig. 5, mounted in recesses 69 in a fixed part 41 of the frame are projected by springs 70 into peripheral recesses 67 formed in a member 65 keyed to the shaft 34. Bolted to the part 41 and enclosing the end of the shaft and the member 65 is a housing 76 shaped to form an annular cylinder 72 for a piston 71 having a projection 78 adapted, when pressure fluid is admitted to the cylinder to bear on the pins 68 and move them out of the recesses 67 thus unlocking the shaft. The supply of fluid to the cylinder 72 from the supply pipe 80 and pipe 81 is under the control of an electrically operated valve similar to that described in Specification 526,307, [Group XXIV], except that the casing contains two members 84, 84a, Fig. 8, each movable along tubular members by rods 103 103a depending from a lever 100 coupled at one end to the armature 107 of a solenoid 106. When the solenoid 106 is energized (and this occurs when the driving motor is switched on) the member 84 is raised and the member 84a lowered against the action of a spring 109. With the valve members in the position shown, fluid from the pipe 81 passes through the member 84 and a pipe 99 to the upper end of a cylinder 105 housing a piston 111 coupled to an electric switch 117. In the other or energized position of the valve members, fluid escapes from the upper part of the cylinder 105 to atmosphere and fluid from the pipe 81 passes through the member 84a to a pipe 82b and thence into the cylinder 72 to unlock the shaft. The cylinder 72 communicates by way of a pipe 113 with the lower end of the cylinder 105 and as the pressure builds up the piston is moved upwardly against a spring 114 to close the switch 117 which is connected in the circuit of a solenoid 118 operating the valve 130 controlling the supply of fluid to the clutch and brake operating cylinder. The valve 130 is supplied with fluid only when the shaft is unlocked, the fluid passing through the cylinder 72, pipe 127 and a valve 120 which is operated by the movement of the piston 71. From the valve 130 it passes to the clutch operating cylinder by way of a pipe 131 and bore 63 in the shaft 34. The valve 120 is connected with a valve 121 through a lever 125 so that when one valve is open the other is closed. The valve 121 admits supply from the pipe 80 through the pipe 129 to the valve 130 when the piston 71 is in its retracted position and the valve 120 closed, to permit the clutch to be used to brake the flywheel by opening the valve 130 by the push button 136. If the motor circuit is broken or if for any other reason the fluid pressure in the cylinder 72 falls below a predetermined level, the spring 114 will operate the switch 117 which cuts off the current supply to the solenoid 118 thereby causing the clutch to be released and the brake applied, while the springs 70 move the pins 68 to lock the shaft. According to whether the shaft is locked or unlocked a finger 144 on the piston 71 operates switches 147 or 146 respectively to give a visual indication on the control panel at 160. After closing the main switch S the machine is started and stopped by means of switches 134 and 135. When the machine is inoperative the button switch 136 enables the clutch to be momentarily engaged to bring the flywheel to rest and inching of the slide may be effected by depressing a button switch 137 and then intermittently operating the switch 138.